I am in the process of buying new speakers, I plan on buying the svs psd 12 sub to go along with them, would full range floor speakers be overkill with a sub, or would there be any benifit to using a full range speaker with a sub, thanks

Your choice-making procedure is, imho, a little backwards. Why decide on having a sub (and a particular one) and then open discussion on the main speakers?

That said, there is an advantage in that (1) using a sub not only increases power handling in the main speakers, it off-loads power demands from the main amps and (2) it allows you to position (and/or EQ) the sub to compensate for room modes while allowing you to position the main speakers for imaging and balance.

I think most floor standers are designed to sound their best alone without subwoofer reinforcement. I just never found the integration to sound as good as a well designed well equipped floor stander, my 2 cents.

There can be benefit with more full range speakers but it depends on the response of the speakers in your room/listening environment and the ability to blend the woofer in a manner that fills in the missing low end without producing excess output at the frequencies the speakers cover. That may require some tricky and hard to achieve crossover parameters. For a more full range speaker, be sure the sub truly can cover the missing very low frequencies down to 15-20 hx or so to start with, otherwise there is no likely benefit save a lot of boomy and poorly defined bass, you know the kind I am talking about, right?

Many smaller and less expensive subs are designed to match better to monitors or other speakers that may only go down to 50-60 hz or so otherwise.

GEtting a smooth blend that truly sounds good can be tricky in any case. That's one reason why educated full range speaker designers make the big bucks! :-)

In general I agree I would start with choosing my full range speakers first and then add a sub later but only one that can be matched well and only if needed, but even then it helps to have the right tools and equipment to measure the results and enable a smooth crossover/blend.

Okay, here's another question. I use Cain & Cain Abby's and a Sophia Baby. I have a NSM 15EXP arriving tomorrow. I will be attempting to make the blend being discussed. Question: run both separate from the speaker taps or use the sub's internal x-over and run amp - sub - speakers?

>I am in the process of buying new speakers, I plan on buying the svs psd 12 sub to go along with them, would full range floor speakers be overkill with a sub,

No.

>or would there be any benifit to using a full range speaker with a sub, thanks

Yes.

1. The short answer is that speakers marketed as "full range" generally aren't. Speaker low frequency extension is specified at low and even potentially inaudible (for the fundamental - with harmonic distortion approaching 100% you can hear the 40Hz second harmonic and 60Hz third harmonic of a 20Hz tone at an inaudible 70dB SPL) levels.

Output at the maximum linear excursion into full space for various representative drivers at 3 feet is as follows at 120, 80, 40, and 20Hz. Many drivers have less excursion and lower output. Subtract 3-5dB for living room dimensions and more for a larger space for the SPL at your listening position

You can add 6dB for a floor mounted woofer (as in many 3-ways), 6dB if there are a pair of bass drivers, and 6dB at the cross-over point to a sub-woofer.

I like to play nice jazz recordings around 85dB SPL average. With 20dB between average and peak levels the speakers are hitting 104-107dB measured at 3 feet. It's a logarithmic scale so that's over 30X the sound power you can get at 120Hz from the 4.5" driver in my chart.

Although you can get speakers with big drivers that only play to 80Hz, consumers want more bass extension so you often need to buy a speaker that plays deeper so you can have sufficient output in the range it'll be playing before it crosses to a sub-woofer.

When it comes to home theater you have the LFE channel which has an extra 10dB of headroom. At movie theater levels you're looking at 115dB SPL peaks at the seats (that could be 1000X the sound power you get from one 10" driver with moderate throw) and even when you keep dialog at a more domestically friendly 60-65dB you're looking at 100-105dB peaks that are 10-100X beyond what you can get. You also have less wiggle room because special effects put a lot of low frequency energy in the last octave compared to music where peaks there are generally at least 10dB down from the rest of the spectrum even in "bass heavy" music.

2. Your brain hears timbre as a weighted combination of what it identifies as a direct sound and its reflections with limited accomodation of high frequency roll-off in the delayed reflections.

When a driver becomes acoustically large with respect to the sound waves it's reproducing at higher frequencies there's less output into the reflections.

You hear changes in the timbre especially where the speaker crosses between acoustically large and small drivers and the high frequency roll-off in the reflections is not monotonic. An 8" driver is large compared to a 4" 3KHz wave and a 1" tweeter small compared to it.

With a "full range" speaker the need for larger bass drivers is more likely to combine with the larger acceptable price tag to net a 3-way with a midrange driver that can remain small acoustically at its cross-over point so the directivity change between midrange and tweeter and impact on timbre is far less significant.

3. People prefer speakers with deeper bass extension (Sean Olive has actually come up with a formula that accurately predicts relative speaker preference with this as a factor), like smaller cabinets, and want to spend less money.

Ported alignments allow designers to have lower bass extension at a given SPL or higher peak SPL for a given bass extension for the same driver displacement (area * stroke) instead of using larger more expensive drivers, 3dB more efficiency out of the same box size or another 1/3 octave extension at the same efficiency, and lower IM and harmonic distortion for the lowest frequencies. This makes ports common.

Unfortunately below the port's tune driver excursion increases far beyond what it would be in a box which nets problems with IM distortion and can even run the driver out to its mechanical limits where it fails after repeatedly banging its voice coil into the motor back plate.

Ported alignments also necessarily introduce more group delay as they approach their low frequency cut-off.

For those reasons ported enclosures tend to integrate better with sub-woofers when crossed over with an electrical high-pass filter an octave above their low frequency cut-off. If you're going to have a ported speaker and want an 80Hz cross-over to a sub-woofer you're better off when the speaker extends to 40Hz.

4. You can get bass which sounds more natural and has fewer measured notches when you augment speakers with sub-woofers (preferably multiples). Earl Geddes probably has the best approach here (commercialized by his company Gedlee and Duke LeJune at Audio Kinesis).

Quality of the bass is also important. My new speakers don't go as low as previous ones, but have more even and natural sounding bass. It is likely that larger drivers interact less with room. Port might be tuned for the lowest distortion and not the extension. Especially attack and decay sound much more natural.

With monitors I would be afraid of poor quality of the upper bass plus hump on the first multiple of port frequency. You can either use not-ported monitors (like Lipinski's), close port or apply filter, before adding a sub. Take into consideration that you might not need sub if you get decent floorstanders and your room provides amplification at right frequency. Distance between walls in my room is about 15' hence 1150/15/2=38Hz (1150 is speed of sound, 2 is because it has to travel back and forth to add) fortifying lowest bass (lowest bass string E=41.2Hz).